Tap changing voltage regulator having means for selecting limits of tap changer motion



Feb.1 1,1969 I L. OAKES ETAL I 3,427,530

TAP CHANGING VOLTAGE REGULATOR HAVING MEANS FOR SELECTING LIMITS OF TAP CHANGER MOTION Filed Oct. 17, 1966 Sheet of 2 VOLTAGE S ENS/N6 MEANS II I LOWEQ RAISE 90 $6 RELAY CONTACT RELAY CONTACT -LowER 1 1 RAISE I. VIII :61412108642'NEUTRAL2aesnolzmIe Feb. 11, 1969 L. CAKES ET AL. 3,427,530

TAP CHANGING VOLTAGE REGULATOR HAVING MEANS FOR SELECTING LIMITS OF TAP CHANGER MOTION 966 Sheet 2 of 2 WMB/ml/g United States Patent Wis.

Filed Oct. 17, 1966, Ser. No. 587,007 US. Cl. 32343.5 20 Claims Int. Cl. H02m /12; H02p 13/06 This invention relates to tap changing voltage regulators and in particular to means for limiting the motion of the tap changer of such a voltage regulator.

Load tap changing voltage regulators are used extensively in the distribution of electrical power to maintain the voltage of a load circuit between predetermined limits, referred to as the bandwidth, regardless of the current drawn by the load and independently of voltage fluctuations of the supply circuit. Such voltage regulators include a winding provided with a plurality of taps connected to stationary contacts on a dial type tap changing switch and a pair of movable contacts adapted to sequentially engage the stationary contacts and connected to the load through an impedance device such as a preventive autotransformer to limit the flow of circulating current when the movable contacts are in a bridging position with regard to adjacent stationary contacts. A common form of tap changer has eight taps in the winding connected to eight stationary contacts of the tap changer dial switch arranged in a circle, a ninth neutral stationary contact, and a pair of movable contacts adapted to rotate in both directions from a neutral position in engagement with the neutral stationary contact to change the voltage over a plus or minus ten percent voltage range in 32 steps of percent voltage. Limit switches are commonly provided to open the circuit to the motor driving the tap changer switch when the switch is in its maximum and minimum positions and thus prevent operation of the tap changer switch beyond its end positions. Further, tap changer position indicating means such as disclosed in US. Patent 3,041,997 to Sidney J. Hartwell, having the same assignee as the present invention, are often used to record the maximum and minimum positions to which the tap changer is operated.

The tap changer can usually be operated at increased load if the range of tap changer operation is decreased and only part of the tapped winding is in the circuit, and mechanical means have been used for changing the range of the tap changer in order to obtain higher current capacity of the tap changing apparatus. However, such mechanical means for selecting tap changer range only permit adjustment of the range at the position indicator and do not permit selection of a smaller range than that corresponding to the tap changer position at the time of range selection. Further, such mechanical range selecting means are relatively complicated and costly and are easily damaged it the position indicator is accidently driven beyond the tap changer range setting or a no-load tap changer slightly overdrives the limiting position.

It is an object of the invention to provide a voltage regulator tap changing apparatus having improved means for selecting the range of the tap changer which permits the range selection to be made either at the voltage regulator or at a remote location. It is a further object of the invention to provide such improved range selection means for a tap changer which will prevent movement of the tap changer switch beyond either the selected range or beyond the maximum and minimum positions. Another object is to provide such an improved tap changer range selector means which will permit selection of a new range of operation even if the tap changer is beyond the newly selected range and which will hold the tap changer within the newly selected range once it returns within the selected range limits. Still another object is to provide such an improved tap chager range selection means which is simpler and less costly than known devices.

These and other objects and advantages of this invention will be more readily apparent from the following detailed description when considered in conjunction with the accompanying drawing wherein:

FIG. 1 is a schematic circuit diagram of a tap changing voltage regulator embodying the invention;

FIG. 2 is a front view of the position indicator of the regulator shown in FIG. 1 with a portion of the indicator dial broken away to show the limit switch and range selection switch means;

FIG. 3 is a front view of the disk of the position indicator of FIG. 2;

FIG. 4 is a side view of the position indicator of FIG. 2 with a portion of the casing broken away to show the internal construction;

FIG. 5 is a schematic diagram illustrating operation of the limit switches by the actuating cam means on the position indicator disk;

FIG. 6 shows one of the limit switches being operated by the cam means on the disk of the position indicator;

FIG. 7 is a cross sectional view through one of the range selection switches; and

FIGS. 8 and 9 are views taken on lines VIIIVIII and IXIX of FIG. 7.

Referring to FIG. 1 of the drawing, a load tap changing voltage regulator of the autotransformer type includes an exciting winding 10 connected across the line to be regulated between the source terminal S and ground and a series winding 11 having a plurality of taps connected to stationary contacts 1-8 and a neutral stationary contact N of a dial type tap changing switch 12. The switch 12 also includes a pair of movable contacts 15 individually operated by a reversible motor 16 through a suitable intermittent motion means 17 and adapted to be selectively positioned on one stationary contact or be positioned in a bridging relationship between adjacent stationary contacts. The movable contacts 15 are connected through a commutator type ring 18 and hub 18' to opposite ends of a preventive autotransformer 19 having its midtap connected to terminal LOAD over which power is supplied to a load. The ends of series winding 11 are connected to stationary contacts of a reversing switch 20 having a movable contact 21 connected by a lead 22 to the neutral stationary contact N and to exciting winding 10 and adapted to connect the series winding 11 in bucking or boosting relation to exciting winding 10 in accordance with the direction of rotation of tap changer switch movable contacts 15 from the stationary neutral contact N. Reversing switch 20 changes the polarity of series winding 11 and therefore doubles the range of the tap changing equipment 12 without changing the voltage steps. Tap changing switch 12 driven by reversible motor 16 through intermittent motion mechanism 17 permits varying the voltage supplied to the load through terminal LOAD over a plus or minus ten percent voltage range in 32 steps of percent voltage.

When the regulated voltage supplied to the load through terminal LOA'D deviates from the bandwidth setting, voltage sensing means (shown in block form) responsive to the regulated voltage and which may include a contact making voltmeter, or voltage control relay, closes a pair of raise contacts -R or a pair of lower contacts L to complete an energizing circuit to the driving motor 16 of the tap changing switch 12 to rotate movable contacts 15 and thus elfect a tap change in the direction to bring the regulated voltage back within the band setting. Tap changer switch 12 may be coupled through suitable motion transmitting means 23 such as a flexible shaft to the driving shaft 24 (see FIG. 4) of a tap changer position indicator 25. The position indicating means of tap changer position indicator 25 is substantially identical to that disclosed in the aforementioned U.S. Patent 3,041,997 to Sidney J. Hartwell and includes a pair of pointers 27 and 28 which indicate respectively the minimum and maximum position to which tap changer switch 12 is operated. Driving shaft 24 is journaled in a position indicator housing 26, and each indicating pointer 27 and 28 carries a tab 30 which is engageable with an instantaneous pointer 31 carried by a rotatable disk, or gear 32 actuated by driving shaft 24. Disk 32 has external teeth 33 which engage a toothed gear 35 affixed to the driving shaft 24. Actuation of driving shaft 24 by tap changer switch 12 during a tap change rotates disk 32 and moves instantaneous pointer 31 affixed thereto across a circular indicating plate 36 mounted in housing 26 and bearing indicia showing the position of tap changer switch movable contacts 15. For example, dial plate 36 may show the letter N indicating the tap changer switch neutral position and markings 1-16R in the clockwise direction and 1-16L in the counterclockwise direction from the neutral position N corresponding to the sixteen tap positions in the boosting and in the bucking directions respectively.

Whenever instantaneous pointer 31 moves past its previous maximum or minimum position, it engages tab 30 on indicating pointer 27 or 28 and moves the indicating pointer to a new maximum or minimum setting. The maximum and minimum indicating members 27 and 28 are maintained in the position in which the instantaneous pointer 31 leaves them by means of clutch assemblies 38 which do not constitute part of the present invention and will not me described, references being made to U.S. Patent 3,041,997 for details of construc tion. Further, resilient spring return means (not shown) are provided to urge the maximum and minimum indicating members 27 and 28 toward the instantaneous indicator 31 when the clutch assemblies are disengaged, and also solenoid means (not shown) are provided to disengage the clutch assemblies and thus reset the position indicating means, but such spring return means and solenoid reset means do not constitute part of the present invention and will not be described in detail.

Position indicator 25 shows the position of the movable contacts 15 of tap changer switch 12 by means of instantaneous pointer 31 aflixed to disk 32 which is mechanically driven from tap changer switch 12 through flexible shaft 23 and driving shaft 24. When disk 32 is rotated through predetermined angles in the clockwise and counterclockwise directions respectively from the neutral position wherein instantaneous pointer 31 is opposite the indicia N, actuating cams 41, 42, 43, 44 and 45 affixed to disk 32 are adapted to open raise limit switches R1, R2 and R3 and lower limit switches L1, L2 and L3 in the circuit of reversible tap changer drive motor 16 to prevent movement of the tap changer switch 12 beyond its maximum and minimum positions and beyond the selected tap changer range. Raise limit switches R1, R2 and R3 and lower limit switches L1, L2 and L3 are supported on the interior and adjacent the lower end of position indicator housing 26. A manually operated raise tap range selection switch 47 and a manually operated lower tap range selection switch 48 adapted to change the range over which the tap changer switch 12 operates in the raise and lower directions respectively may also be mounted on position indicator housing 26, or the raise and lower range selection switches 47 and 48 may be mounted at ground level when the voltage regulator is mounted on a pole, or switches 47 and 48 can be mounted at any desired location remote from the voltage regulator.

Each raise limit switch Rl-R3 and each lower limit switch L1-L3 is a commercially available miniature electrical switch having a pair of normally closed contacts 49 (see FIG. 1) enclosed in an insulating housing 50 (see FIGS. 2 and 4) and an actuating arm 51 provided with a curved end portion and adapted to open the normally closed pair of contacts 49 when a radially directed force exerted against the curved end portion depresses arm 51. The actuating cams 41-45 on disk 32 are adapted to exert a radial force on the curved end portions of arms 51 and selectively depress the actuating arms 51 on raise limit switches R1-R3 and on lower limit switches L1-L3 when disk 32 is rotated through predetermined angles in the clockwise and counterclockwise directions respectively from the neutral position to open the normally closed contacts 49. The cams 41-45 can move in both directions past the actuating arms 51 without damaging the limit switches, and it will thus be appreciated that the range selection means will not be damaged if the position indicator is accidentally driven beyond the range setting. The three raise limit switches Rl-R3 are mounted side by side on an Lshaped bracket 53 affixed by suitable means such as spot welding to the interior surface of position indicator housing 26 and to the right side of the axis of disk 32 as seen in FIG. 2, and similarly the three lower, or bucking limit switches L1L3 are mounted side by side on a similar L-shaped bracket 53 (not shown) affixed to the interior of position indicator housing 26 and to the left side of the axis of disk 32.

The limit switch actuating cams 41-45 are secured at arcuately spaced apart positions on disk 32, and actuating earns 42 and 44 protrude further in an axial direction than cams 41, 43 and 45 and are the only actuating cams which engage the arcuate end portions of actuating arms 51 of lower switch L3 and raise switch R3 when disk 32 is rotated. The raise limit switch R2 is reversed in its mounted position relative to raise limit switches R1 and R3 so that its actuating arm 51 is displaced two positions from the actuating arms of raise switches R1 and R3, and similarly the lower limit switch L2 is reversed in its mounted position relative to the lower limit switches L1 and L3.

Each manually operated raise" and lower tap range selection switch 47 and 48 includes five stationary contacts designated A, B, C, D and E. The stationary contacts A, B and C of manual raise switch 47 are connected to the raise limit switches R1, R2 and R3 respectively, and the stationary contacts A, B and C of manual lower switch 48 are connected to the lower limit switches L1, L2 and L3, respectively. Stationary contacts D and E of raise switch 47 are connected by leads 60 and 61 to raise limit switches R2 and R3, respectively, and stationary contacts designated D and E of lower switch 48 are connected by leads 62 and 63 to limit switches L2 and L3, respectively. Each manually operated raise switch 47 and lower switch 48 also includes a pair of arcuately spaced rotatable contacts 65 and 66 adapted to engage the stationary contacts A, B, C, D and E. The raise and lower switches 47 and 48 are manually set to select a 5, 6%, 7 /2, 8% and 10 percent voltage range of the tap changer switch in the raise and lower directions when the rotatable contacts 65 of switches 47 and 48 engage the stationary contacts A, B, C, D and E respectively. When rotatable contact 6 5 of raise switch 47 engages stationary contact A, it connects limit switch R l in the forward energizing circuit to motor 16, and actuating cam -41 is adapted to operate limit switch R1 when tap changer switch movable contacts 15 have been rotated in a clockwise direction into engagement with tap changer switch stationary contact 4, corresponding to a five percent voltage boost, to prevent further rotation of movable contacts 1'5 in a clockwise direction. When rotatable contact 65 of lower switch 48 engages stationary contact A, it connects limit switch L1 in the reverse energizing circuit to motor 16, and actuating cam 45 is adapted to operate limit switch L1 when tap changer switch movable contacts 15 have been rotated in a counterclockwise direction into engagement with stationary contact 5, corresponding to a five percent bucking voltage, to prevent marking 6R to marking 14R so that cam 41 is opposite arm 51 of limit switch R1 and depresses arm '51 to open contacts 49 of limit switches R1 and interrupt the energizing circuit to motor 16. The tap changer switch confurther rotation of movable contacts 15 in the counter- 5 tacts 15 thus cannot be actuated beyond tap changer clockwise direction. switch stationary contact 4 corresponding to a 5 percent FIG. 5 represents that the angular movement of actuvoltage boost unless the raise range selector switch 47 ating cams 41-45 occurs in the plane of the paper and is reset to a higher selection position such as 6% percent shows such angular cam movement as linear displaceboost wherein movable contact 65 engages the stationary ment to the left and right of neutral position N as disk 10 contact designated B. it will be noted that actuating cam 32 carrying instantaneous pointer 31 and cams 41- 45 41 does not extend far enough in an axial direction 10 rotates in the counterclockwise and clockwise directions actuate arm 51 of limit switch R3. It will also be noted respectively. FIG. 5 illustrates actuating cams 41-45 in that p changer Switch 12 can be actuated to 3 Position the neutral position, and it will be noted that cam 41 is Wheffihl the Voltage bOOSt is less than 5 Percent and opposite marking 6R on dial plate '36 corresponding to 15 motor can energized to actuate p changer 12 in i tap changes in the boosting direction f the the counterclockwise direction through lower contact L tral position, cam 42 is opposite marking 2R, cam 43 of the contact making voltmeter and limit switch L1 of is opposite marking N, cam 44 is opposite marking 2L bucking Tahge Selection Switch d cam 45 i opposite ki 6L on di plate 36 Assume now that the raise range selection switch 47 Further, limit switch Ll-L3 and R1-R3 are mounted on 1S adlusted to actuate movable Contact 65 into position indicator housing 26 so that the actuating arms Iheht With Stationary control designated B Corresponding 51 of limit switches R1 and R3 are opposite marking 14R, to a 6% percent voltage boost If the regulated voltage is actuating arm 51 f E i i h R2 i p i marking still below the lower bandwidth setting, tap changer motor 16R, th actuating arms 51 f li i it h L1 d L8 16 is energized through contacts 49 of limit switch R2 and are opposite marking 14L, and actuating arm 51 of limit raise ontacts R of the contact making voltmeter to switch L2 is opposite marking 16L corresponding to sixactuate movable contacts 15 of the tap changer switch teen tap changes of contacts 15 in the counterclockwise 12 in the clockwise direction through two tap changes and bucking direction from neutral position N wherein tap into engagement With p Changer Switch Stationary c011- changer switch movable contacts 15 are in engagement ta t 5. AS tap changer switch 12 rotates through two with tap changer switch stationary contact 1. 30 additional tap changes in the clockwise direction, disk 32 The following table shows the limit switches Ll-LB is rotated clockwise and moved two positions to the right d vR1 R 3 whi h r operated b th cams 41-45 to as shown in FIG. 2 so that cam 41 now is opposite markopen the energizing circuit to tap changer motor 16 ing 16R and depresses arm 51 of limit switch R2 to open when the range selector switches 47 and 48 are set at contacts 49 of limit switch R2 and deenergize motor 16. thepositions indicated: When raise range selection switch 47 is set to engage Lower Switch 48 Position Raise Switch 47 Position Limit Switch E D C B A A B C D E X X X X X X X X X X X X X X Percent Tap Range Assume that the range over which the tap changer is movable contact 65 with stationary contact C, tap changer selected to operate is plus or minus 5 percent voltage, motor 16 may be energized through contacts 49 of raise which corresponds to eight tap changes of /8 percent limit switch R3 and contacts R of the contact making voltage from neutral position in the clockwise and the voltmeter if the regulated voltage deviates below the lower counterclockwise directions. For this selected range of band setting. Motor 16 may then actuate movable contap changer operation, the raise and lower range selectacts 15 clockwise individually through two tap changes tion switches 47 and 48 are adjusted as shown in FIG. 1 and into engagement with tap changer switch stationary with switch arms of both switches 47 and 48 in encontact 6 and rotate disk 32 further clockwise until cam gagement with range selection switch stationary contacts 42 is opposite marking 14R and depresses the actuating A so that power to motor 16 flows through contacts 49 arms 51 of raise limit switches R1 and R3 and frees arm of limit switches R1 for boosting operation and through 51 of raise limit switch R2 to interrupt the energizing limit switch 1 for bucking operationh n he r i circuit to motor 16 and thus prevent actuation of ta contacts R of the contact making voltmeter close due to the regulated voltage being below the lower bandwidth setting, motor 16 actuates tap changer switch contacts 15 in the raise direction and rotates disk 32 carrying cams 41-45 clockwise so that cams 41-45 move to the right as shown in FIG. 5. When both tap changer movable contacts 15 have been moved eight 41% voltage steps clockwise and are in engagement with tap changer switch stationary contact 4, cam 41 has been moved eight positions to the right as shown in FIG. 5 from changer switch 12 past the position corresponding to 7 /2 percent boost wherein tap changer switch movable contacts 15 have been rotated through 12 tap changes in the clockwise boosting direction from the neutral posi tion N.

If raise range selection switch 47 is now manually set to engage movable contact 65 with stationary contact D and movable contact 66 with stationary contact A, an energizing circuit to motor 16 may be completed through limit switches R1 and R2 in parallel and through contacts R of the contact making voltmeter if the regulated voltage is still below the lower bandwidth limit. Motor 16 may now actuate the tap changer movable contacts 15 individually until both engage tap changer switch stationary contact 7 corresponding to an 8% percent voltage boost and fourteen tap changes of percent voltage in the clockwise boosting direction from the neutral position. Tap changer switch 12 also actuates disk 32 further clockwise until cam 42 is opposite marking 16R and depresses arm 51 of raise limit switch R2 and cam 43 is opposite marking 14R and depresses arm 51 of limit switch R1. With contacts 49 of both limit switches R1 and R2 open, the circuit of tap changer motor 16 is interrupted to prevent further rotation of tap changer switch movable contacts 15 in a clockwise direction to boost the voltage.

If raise range selector switch 47 is now manually adjusted so that movable contacts 65 and 66 engage stationary contacts respectively designated E and B, as shown in dotted lines in FIG. 1, tap changer motor 16 may be energized through limit switches R2 and R3 in parallel and through contact R of the contact making voltmeter to rotate movable contacts 15 further in a clockwise direction if the regulated voltage is still below the lower bandwidth. Motor 16 may rotate both movable contacts 15 to the maximum boost position wherein both engage tap changer switch stationary contact 8, and tap changer switch 12 also rotates disk 32 clockwise and to the right as shown in FIGS. 2 and until cam 43 is opposite marking 16R and depresses arm 51 of limit switch R2 and cam 44 on disk 32 is opposite marking 14R and depresses actuating arms 51 of limit switches R1 and R3 so that the contacts 49 of all raise limit switches R1-R3 are open, thereby deenergizing motor 16 and preventing further motion of tap changer switch 12 in the clockwise direction. It will be noted that with all three raise limit switches R1-R3 open, it is impossible to energize motor 16 to drive tap changer switch 12 further in the voltage boost direction, thereby providing an additional safety feature. The only direction in which tap changer switch 12 can now be actuated is in the counterclockwise direction to lower the voltage.

The above description covers movement of tap changer switch 12 in a clockwise direction to raise the voltage, but operation of tap changer switch 12 and disk 32 carrying cams 4145 in the counterclockwise bucking direction from the neutral position is substantially identical to that described above with the exception that disk 32 moves to the left as seen in FIG. 5, and consequently operation of the apparatus in the direction to provide bucking voltage will not be described in detail.

Raise and lower range selection switches 47 and 48 are identical and may be commercially available rotary dial switches mounted either on position indicator housing 26 or at a remote location. Only one switch 47 will be described. As shown in FIGS. 7, 8 and 9, range selector switch 47 is disposed internally of position indicator housing 26 and includes an operating shaft 70 extending axially through the bore in an externally threaded mounting stem 71 which protrudes through a clearance hole 72 in housing 26. A nut 74 engages the external threads on mounting stem 71 to secure switch 47 to housing 26. A pair of screws 75 extending through clearance holes in a plate 76 secured to mounting stem 71 support an annular sta tionary contact mounting plate 78 of insulating material. A plurality of stationary conductive contacts 80 are mounted in arcuately spaced positions on insulating plate 78 by suitable means such as rivets, some of the stationary contacts 80 being mounted on one side of insulating plate 78 and other stationary contacts 80 being mounted on the opposite side of insulating plate 78. A pair of circular movable metallic contacts 82A and 82B disposed on 0pposite sides of a circular insulating member 79 coaxial with and rotatable within annular insulating plate 78 have noncircular central apertures 83 which receive a comple mentary noncircular portion 84 on the end of operating shaft 70 to provide a driving connection therebetween. The two movable contacts 82A and 82B are electrically connected together by prongs 94 on these contacts ex tending through circular member 79, and the upper and lower movable contacts 82A and 82B have arcuately spaced apart, radially extending projections 65 and 66 thereon, respectively, which are shown as rotatable arms in FIG. 1. The radial projections 65 and 66 are adapted to enter between opposed jaws 88 on the stationary contacts as operating shaft 70 carrying movable contacts 82A and 82B is manually actuated, and the upper circular contact 82A rotates within and maintains continuous electrical contact with a stationary jaw contact 89 mounted on insulating plate 78 and connected by a lead 90 (see FIG. 1) to the raise contact R of the contact making voltmeter. A hand knob 92 affixed to the end of operating shaft 70 external of position indicator housing 26 carries an arrow which cooperates with the markings-5, 6%, 7 /2, 8% and 10 (not shown) on an indicia plate 93- surrounding operating shaft 70 to visually display the tap range selector switch setting in the raise direction.

The disclosed apparatus permits selection of the limits of operation of a voltage regulator tap changer either at the position indicator or at ground level if the regulator is mounted on a pole. The disclosed invention permits selection of a smaller range of tap changer operation to obtain an increase in the current carrying capacity of the tap changer, and such selection can be made without concern as to whether the tap ohanger is within the newely selected range of operation since the actuating arms 51 of the limit switches are depressed radially and the actuating cams 41-45 can move in both directions past the limit switches. This feature also assures that the disclosed device is not damaged if the position indicator is accidentally driven through a selected limit position or if a no-load tap changer slightly overrides the limiting position.

When only a single embodiment of the invention has been illustrated and described, many modifications and variations thereof will be readily apparent to those skilled in this art. For example, it will be apparent that the disclosed limit switches and cam means for operating the limit switches can be replaced respectively by switches of the reed type and magnetic means carried by rotatable disk 32 for operating the reed switches at dilferent predetermined tap positions. Consequently it is intended in the appended claims to cover all such modifications and variations which are within the true spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination with a voltage regulator having a winding provided with taps, a tap changer switch having stationary contacts connected to said taps and movable contacts adapted to engage said stationary contacts, a reversible motor for driving said tap changer movable contacts in opposite directions from a neutral position through intermediate tap positions to maximum and minimum positions wherein the regulated voltage has maximum and minimum values respectively, means including voltage sensing means and raise and lower contacts controlled by said sensing means for completing forward and reverse energizing circuits to said motor in response to deviations of the regulated voltage above and below the voltage bandwidth setting;

first and second normally closed raise switching means,

first and second normally closed lower switching means,

raise range selector means for selectively connecting said first and second raise switching means in the forward energizing circuit to said motor,

lower range selector means for selectively connecting said first and second lower switching means in the reverse energizing circuit to said motor, and

means for opening said first raise and first lower switching means when said tap changer switch movable contacts are in said maximum and minimum positions respectively and for opening said second raise and second lower switching means when said tap changer switch movable contacts are actuated to predetermined intermediate tap positions in the forward and reverse directions respectively.

2. In combination with a voltage regulator having a winding provided with taps, a tap ohanger switch having stationary contacts connected to said taps and movable contacts adapted to engage said movable contacts, a motor for operating said movable contacts, means including voltage sensing means for completing an energizing circuit to said motor when the voltage regulated by said regulator deviates beyond a predetermined limit,

a plurality of normally closed switching means,

manually operable tap changer range selector means for selectively connecting said switching means in said energizing circuit to said motor,

and means actuated by said tap changer switch for successively opening said normally closed switching means in response to rotation of said tap changer switch movable contacts into engagement with predetermined tap changer switch stationary contacts, whereby the range over which said tap changer switch operates may be adjusted by said manually operable range selector means.

3. The combination defined by claim 2 and including indicating means for visually displaying the position of said tap changer switch movable contacts and wherein said indicating means includes a rotatable member actuated by said tap changer switch and carrying said means for successively opening said switching means.

4. The combination defined by claim 3 wherein said means for opening said switching means includes cam means carried by said rotatable member and said switching means are limit switches having operating arms actuable in a direction radial of said rotatable member to open said switches and said operating arms are in the path of movement of said cam means and are actuated in said radial direction when said cam means are rotated into engagement therewith, whereby said cam means can move in both directions past said limit switches and no damage occurs if said tap changer switch is accidentally driven beyond a limit position.

5. In combination with a voltage regulator having a winding provided with taps, a tap changer switch having stationary contacts connected to said taps and movable contacts adapted to engage said stationary contacts, a reversible motor for driving said tap changer movable contacts in opposite directions from a neutral position through intermediate tap positions to maximum and minimum positions wherein the regulated voltage has maximum and minimum values respectively, means including voltage sensing means and raise and lower contacts controlled by said sensing means for completing forward and reverse energizing circuits to said motor in response to deviations of the regulated voltage above and below the voltage bandwidth setting;

normally closed first and second raise limit switches,

a raise range selector switch for selectively connecting said raise limit switches in the forward energizing circuit to said motor,

normally closed first and second lower limit switches,

a lower range selector switch for selectively connecting said lower limit switches in the reverse energizing circuit to said motor,

and cam means actuated by said motor for operating said first raise and said first lower limit switches when said tap changer switch movable contacts are in said maximum and minimum positions respectively and being adapted to operate said second raise and said second lower limit switches when said movable contacts are in first predetermined intermediate tap positions in the forward and reverse directions respectively.

6. In the combination defined by claim 5 and including means for indicating the position of said tap changer movable contacts and wherein said indicating means includes a. rotatable member driven by said motor and carrying said cam means.

7. The combination defined by claim 6 wherein said limit switches have operating arms actuable in a direction radial of said rotatable member to open said switches and said operating arms are in the path of movement of said cam means and are actuated in said radial direction when said cam means are rotated into engagement therewith.

8. In the combination defined by claim 5 and including a third normally closed raise limit and a third normally closed lower limit switch and wherein said raise range selector switch selectively connects said three raise limit switches in the forward energizing circuit to said motor and said lower range selector switch selectively connects said three lower limit switches in the reverse energizing circuit to said motor and said cam means are adapted to operate said third raise and said third lower limit switches when said tap changerswitch movable contacts are in second predetermined intermediate tap positions in the forward and reverse directions respectively.

9. In the combination defined by claim 8 wherein said first and third raise limit switches are at the same location and are arcuately spaced from said second raise limit switch and said cam means includes a rotatable member driven by said motor and carrying first and second arcuately spaced apart cams, the first cam being adapted to operate only said first and second raise limit switches and said second cam being adapted to operate all three raise limit switches.

10. In the combination defined by claim 9 wherein said raise range selector switch has four positions in the first, second and third of which it selectively connects in the forward energizing circuit to said motor said first, second and third raise limit switches and in the fourth position of which it connects said first and second raise limit switches in parallel in the forward energizing circuit to said motor and wherein said cam means also includes a third cam carried by said rotatable member in arcuately spaced relation to said second cam, said second and third cams being adapted to simultaneously operate said first and second raise limit switches.

11. In the combination defined by claim 10 wherein said raise range selector switch has a fifth position in which it connects said second and third raise limit switches in parallel in the forwarding energizing circuit to said motor and wherein said cam means includes a fourth cam carried by said rotatable member in arcuately spaced relation to said third cam and adapted to operate said first and third raise limit switches simultaneously with the operation of the second raise limit switch by said third cam.

12. In the combination defined by claim 11 wherein said first and third lower limit switches are at the same location and are arcuately spaced from said second lower limit switch and said cam means also includes a fifth cam carried by said rotatable member in arcuately spaced relation to said fourth cam and wherein said raise limit switches are operated by said cam means upon actuation of said rotatable member in one direction from a neutral position corresponding to the engagement of said tap changer switch movable contacts with said stationary neutral contact and said lower limit switches are operated by said cam means upon actuation of said rotatable member in the opposite direction from said neutral position and wherein said fifth cam is adapted to operate only said first and second lower limit switches and second fourth cam is adapted to operate all three lower limit switches.

13. In the combination defined by claim 12 wherein said lower range selector switch has five positions in the first, second and third of which it selectively connects said first, second and third lower limit switches in the reverse energizing circuit to said motor, in the fourth position it connects said first and second lower limit switches in parallel in said reverse energizing circuit and wherein said third cam is adapted to operate only said first and second lower limit switches when said rotatable member is actuated in said opposite direction and is adapted to operate said first lower limit switch simultaneously with the actuation of said second lower limit switch by said fourth cam and said second cam is adapted to operate said first and third lower limit switches simultaneously with the operation of said second lower limit switch by said third cam.

14. In the combination defined by claim 13 and including means for visually displaying the position of said tap changer switch movable contacts and wherein said displaying means includes a pointer carried by said rotatable member.

15. In the combination defined by claim 9 wherein said third raise limit switch is spaced a greater distance in an axial direction from said rotatable member than said first and second raise limit switches and wherein said second cam has a greater length in the axial direction than said first cam.

16. In the combination defined by claim 13 wherein said third raise and third lower limit switches are spaced a greater distance in said axial direction from said rotatable member than said first and second raise and first and second lower limit switches and all five of said cams project from said rotatable member in a direction parallel to the axis thereof and wherein said second and fourth cams extend a greater distance in the axial direction than said first, third and fifth cams.

17. In the combination defined by claim 11 wherein said range selector switch has five stationary contacts spaced apart in an arc and a pair of electrically connected movable contacts adapted to engage said stationary contacts and arcuately spaced apart by an angle approximately equal to the angle subtended by four of said stationary contacts.

18. In the combination defined by claim 14 wherein said visual displaying means includes a housing carrying a dial plate marked with indicia which cooperates with said pointer to indicate the position of the tap changer switch movable contacts, journal means in said housing for rotatably supporting said rotatable member, and wherein said raise and said lower limit switches are mounted on said housing.

19. In the combination defined by claim 14 wherein said third cam is approximately in radial alignment with said pointer and said second and fourth cams are arcuately spaced in opposite directions from said third cam by twice the angle through which said rotatable member is actuated during a tap change and said first and fifth cams are arcuately spaced in opposite directions from said third cam by six times the angle through which said rotatable member is actuated during a tap change and wherein only said second and fourth cams are capable of operating said third raise and said third lower limit switches.

20. In the combination defined by claim 11 wherein said rotatable member is rotated through an angle A during each tap change and said second and fourth cams are arcuately spaced in opposite directions from said third cam through an angle 2A and said first cam is arcuately spaced from said third cam by an angle equal to 6A.

References Cited UNITED STATES PATENTS 2,680,832 6/1954 Schultz 323-43.5 3,235,788 2/1966 Riebs 32343.5 3,237,091 2/1966 Attewell 32343.5 3,252,078 5/1966 Conner 323-43.5 3,366,763 1/1968 Bleibtreu et a1. 323-435 X 3,381,213 4/1968 Rice et al 323-435 JOHN F. COUCH, Primary Examiner.

G. GOLDBERG, Assistant Examiner.

US. Cl. X.R. 32347 

1. IN COMBINATION WITH A VOLTAGE REGULATOR HAVING A WINDING PROVIDED WITH TAPS, A TAP CHANGER SWITCH HAVING STATIONARY CONTACTS CONNECTED TO SAID TAPS AND MOVABLE CONTACTS ADAPTED TO ENGAGE SAID STATIONARY CONTACTS, A REVERSIBLE MOTOR FOR DRIVING SAID TAP CHANGER MOVABLE CONTACTS IN OPPOSITE DIRECTIONS FROM A NEUTRAL POSITION THROUGH INTERMEDIATE TAP POSITIONS TO MAXIMUM AND MINIMUM AND SITIONS WHEREIN THE REGULATED VOLTAGE HAS MAXIMUM AND MINIMUM VALUES RESPECTIVELY, MEANS INCLUDING VOLTAGE SENSING MEANS AND RAISE AND LOWER CONTACTS CONTROLLED BY SAID SENSING MEANS FOR COMPLETING FORWARD AND REVERSE ENERGIZING CIRCUITS TO SAID MOTOR IN RESPONSE TO DEVIATIONS OF THE REGULATED VOLTAGE ABOVE AND BELOW THE VOLTAGE BANDWIDTH SETTING; FIRST AND SECOND NORMALLY CLOSED RAISE SWITCHING MEANS, FIRST AND SECOND NORMALLY CLOSED LOWER SWITCHING MEANS, RAISE RANGE SELECTOR MEANS FOR SELECTIVELY CONNECTING SAID FIRST AND SECOND RAISE SWITCHING MEANS IN THE FORWARD ENERGIZING CIRCUIT TO SAID MOTOR, LOWER RANGE SELECTOR MEANS FOR SELECTIVELY CONNECTING SAID FIRST AND SECOND LOWER SWITCHING MEANS IN THE REVERSE ENERGIZING CIRCUIT TO SAID MOTOR, AND MEANS FOR OPENING SAID FIRST RAISE AND FIRST LOWER SWITCHING MEANS WHEN SAID TAP CHANGER SWITCH MOVABLE CONTACTS ARE IN SAID MAXIMUM AND MINIMUM POSITIONS RESPECTIVELY AND FOR OPENING SAID SECOND RAISE AND SECOND LOWER SWITHCING MEANS WHEN SAID TAP CHANGER SWITCH MOVABLE CONTACTS ARE ACTUATED TO PREDETERMINED INTERMEDIATE TAP POSITIONS IN THE FORWARD AND REVERSE DIRECTIONS RESPECTIVELY. 